My guess: It's because he thinks he'll make a good president.
This being said ...
Remember Bill Clinton's "fall in line" speech from the Iowa picnic? I bet he did not suspect that this particular speech would be seen by so many, over C-SPAN, or that it would become part of the institutional memory of people watching the 2004 presidential campaign.
There was some good stuff in that speech ... as well as some poison.
We all remember what the poison was, but I think that the good stuff has been all but passed over.
What Bill Clinton emphasized in this speech (and others) was that Democratic presidential campaigns have to be about ideas. They have to be about policy.
The Republican party can win just for the sake of winning. They can with just with their checkbooks. They can win when elections are just about power. But for Democrats, running a campaign on this kind of basis just won't work.
I think that the reasons for this are many, but the two that stick out most in my mind are 1) the demographic differences between Republican and Democratic voters and 2) Democratic voters will only tepidly support a candidate that they do not perceive as wanting to do something good for the country.
The second item above is the most important one. Democrats want their president to accomplish something, to make a positive change, to make things better for people who live in the country. The Republican platform does not reflect these kind of goals. They want the government to do less, while controlling more. Scary, but true ...
I think that this is what Kos and others are hinting at when they say that they have no idea why Kerry is running for president. For some reason or another, his candidacy, as presented in the media, is not a candidacy of ideas in the same way that that of Bill Clinton -- or even Howard Dean or John Edwards -- was.
John Kerry was cast in the mold of the perfect tabula rasa ABB candidate after Iowa. This propelled him to near universal primary victories. But to beat Bush in November, he has to be something more than just a blank slate onto which we can project our expectations. This might have worked for primary voters, but it is hard to see how it will work in the general election.
